Engine/Transmission (1998.5 - 2002) Engine "sound" different W/ Cruise on! (less rattle)

[paulsmith]

2001 HO 6 speed 3500, new engine at 192000 miles, (now 225000) F1 injectors, but otherwise stock.



When driving with the "gas pedal" the engine is loud, rattles, like a diesel. Louder than my 96 for sure, always has been. More throttle, louder it gets, let off and it is not a loud... normal.



BUT, if I put on the Cruise Control, the "knock" drops off noticeably. I can hold the "Accel" button down, truck speeds up, ands it gets louder, but not as loud as if I use the pedal.



I mean engine "tone" changes if I just TOUCH the pedal in the floor (don't even move it) with the Cruise Control on. Almost funny...



Does timing change with pedal control vs cruise control? what is causing this very noticeable sound change? It depends on where the injection pump gets its control signal from.



Paul Smith

www.NeedaTrailer.com

 

[SWC]

Paul, I have 01. 5 3500 with the 6 speed as well. I have around 230,000 miles on the truck. I have noticed this sound as well. My assumption is that the vibration of the mighty Cummins is brought into the cab through the throttle cable when there is tension on it. When on cruise the tension is released at the APPS. When the cruise is engaged apply pressure on the foot throttle and the sound comes back. Release and the sound is gone. The sound difference is not overwhelming, but I do notice it. Someone riding in the right seat cannot hear it. I have asked.

Stan

 

[Ragain]

I agree w/ SWC. I get the same sound transferred through throttle cable when my foot rests on the pedal. Isn't very noticable unless I listen for it though.

 

[obert]

Same here, too. My ol' truck still has cruise in the PCM.